Biological joints can degrade over time, deteriorate as a result of a birth defect or a disease, become damaged as a result of an accident or unwarranted motion, malformations due to incorrect growths, and the like. As the joint deviates from a normal, mobile condition, the malformed joint can cause multiple issues to the individual or animal, including sporadic or constant pain, limited motion, any degree of incapacitation, and the like.
Common joints that require surgical attention include inter-vertebrae discs, hips, knees, shoulders, elbows, and the like.
Inter-vertebrae discs can degrade over time or become damaged where they no longer function properly. The defective inter-vertebrae discs allow unwarranted motion between two adjacent vertebrae. The defective inter-vertebrae discs limit or reduce the support along the individual's spine. Over time, the defective inter-vertebrae disc needs surgical attention. Inter-vertebrae discs are addressed by fusing two or more adjacent vertebrae together. One short-term drawback of this procedure is the resulting limitation of motion incurred by the individual. A long-term drawback is that over time, the fused region increases stresses on adjacent joints, resulting in additional surgical procedures to fuse other regions of the individual's spine.
Other joints, such as hips and shoulders, are commonly formed having a first end of one bone moveably engaged with a mating end of a mating bone. Most joints comprise a first joint member formed in a ball and the mating joint member formed in a socket. As either or both of the surfaces of the joint members wears or deteriorates, the support of the joint degrades, hindering the mobility of the individual. In addition to the reduced mobility, the deteriorating joint can cause inflammation, discomfort, and other unwanted physical and psychological issues.
A few material compositions are known that have a unique property, a reversible, solid-state phase transformation known as a martensitic transformation. One of these material compositions is Nickel titanium, also known as nitinol. Nitinol is a metal alloy of nickel and titanium, where the two elements are present in roughly equal atomic percentages.
Nitinol alloys exhibit two closely related and unique properties: shape memory and superelasticity (also called pseudoelasticity). Shape memory refers to the ability of nitinol to undergo deformation at one temperature, and then recover its original, undeformed shape upon heating above its “transformation temperature”. Superelasticity occurs at a narrow temperature range below its transformation temperature; in this case, no heating is necessary to cause the undeformed shape to recover, and the material exhibits enormous elasticity, some 10-30 times that of ordinary metal. The elasticity commonly occurs at a lower temperature, where the material recovers to its original shape upon returning to an ambient temperature.
Nitinol has an additional benefit, where the material is conducive to medical applications. The material can be surgically implanted into a patient with very limited risk of biological rejection.
Therefore, what is desired is a device capable of being surgically implanted to repair or overcome medial deficiencies of a damaged or defective biological joint.